Hi Bill,
The bandwidth requirements vary depending on what Codec is being used. Here is some related info. The first doc has a good link to the TAC Voice Bandwidth Calculator which is very helpful;
Voice Over IP - Per Call Bandwidth Consumption
http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a0080094ae2.shtml
Q. What are the voice bandwidth requirements for different codecs?
A. Voice bandwidth requirements are:
G.711 - 106 Kbps (50 pps, 200 byte long packets)
G.729 - 44 Kbps (34 pps, 60 byte long packets) (default)
G.723 - 30 Kbps (34 pps, 64 byte long packets)
http://www.cisco.com/en/US/products/hw/routers/ps380/products_qanda_item09186a0080093e46.shtml#qa2
Hope this helps!
Rob
